This invention relates generally to a heat exchange assembly or apparatus for use in conjunction with a liquid-cooled internal combustion engine employed in a motor vehicle and, more particularly, to a new and improved heat exchange apparatus which includes a toroidal-type radiator assembly including an annular core having radially extending, air cooling passageways formed therethrough, rotary fan means for inducing an air stream, and a contoured fan shroud structure for directing the fan-induced air stream radially through the radially extending, cooling air passageways of the annular radiator core efficiently without a significant reduction in the velocity pressure of the fan induced air stream caused by redirection thereof from an axial direction to a radial direction when the rotary fan means is of the blower type or, from a radial direction to an axial direction when the rotary fan means is of the suction type. This invention also contemplates the provision of an auxiliary or secondary radiator structure positioned with respect to the rotary fan and fan shroud structure in such a manner that a portion of the fan-induced air stream is caused to flow through the cooling air passageways of the core of the auxiliary radiator structure. The heat exchange apparatus of the present invention is also effective to cause the velocity of the air stream passing through the radiator core to be substantially uniform axially across the cylindrical air intake face of the radiator core.
Most vehicles generally in use today, such as passenger cars and motor trucks, are propelled by internal combustion engines and such engines, as is well known, generate heat during the operation thereof. For the most part, the motor vehicle internal combustion engines employed are of the liquid-cooled type which entail the circulation, under pressure, of a coolant through the engine for absorbing heat. The correct operating temperature of the engine is maintained by subsequently and sequentially passing, under pressure, the heated coolant received from the engine through a heat exchange system or apparatus for dissipating heat from the coolant to the atmosphere and returning the coolant to the engine for recirculation therein. Generally, the heat exchange apparatus employed includes a heat exchanger or radiator through which the heated coolant received from the engine is caused to flow. Simultaneously, cooling air is also caused to flow through the radiator which absorbs heat from the heated coolant and carries it out into the atmosphere.
The cooling capacity of a heat exchange apparatus is dependent upon many factors including the velocity and volume of the air caused to flow through the radiator core as well as the distribution pattern of the air stream over the available heat exchange surface of the radiator core. Ideally, to achieve the highest heat transfer efficiency of any heat exchange apparatus, it is desirable that the velocity of cooling air flowing through the radiator core be uniformly distributed over the entire available heat exchange surface of the radiator core. The heat exchange apparatus almost universally found in conventional motor vehicles propelled by liquid-cooled internal combustion engines involves a radiator or heat exchanger assembly which has a flat, generally rectangularly-shaped core structure. The radiator is usually oriented so as to be generally upright and is positioned axially forwardly of the engine. The heat exchange apparatus of conventional motor vehicles also includes, for the most part, a rotary fan of the axial flow, suction type which is usually positioned between the engine and the flat radiator. The fan is designed to suck or draw air from the atmosphere forwardly of the radiator structure and cause the air stream induced thereby to flow substantially axially through the radiator. Heretofore, in most motor vehicle installations, the air stream after passing through the radiator core was discharged back over the engine which, as pointed out hereinbefore, is usually spaced axially rearwardly of the fan and radiator structure.
The rotary fan used in most motor vehicle engine heat exchange apparatuses for propelling the cooling air through the radiator core includes a multi-bladed rotor. The fan impeller blades extend radially from the fan hub and thus the fan blade tips circumscribe a circle when the fan is being operated. Because the cooling air intake and discharge faces of the flat radiator core are rectangular in shape and since the fan blade tips circumscribe a circle, the air flow distribution pattern is not uniform over the entire available area of the flat radiator core. In fact, it has been found that very little, if any, of the cooling air stream induced by the fan actually passes through the four corner face areas of the radiator core. The addition of a conventional venturi type fan shroud to the heat exchange installation in an attempt to minimize velocity pressure losses of the air stream does little, if anything, toward the problem of improving the air flow at the four corner areas of the radiator core air intake face.
Automotive cooling system engineers have long been intrigued with the possibility of overcoming the aforementioned operational shortcomings as well as other inherent and well known heat transfer deficiencies of traditional automotive heat exchange systems by using a toroidal type heat exchanger in lieu of the conventional flat, radiator. In a toroidal heat exchanger the radiator core is, in effect, wrapped around the fan and resembles a drum shell with the air stream intake and discharge faces of the radiator core in the form of radially spaced and parallel concentric cylinders. The fan, which is encircled by the radiator core, may be a blower type wherein cooling air is drawn axially from one axial side of the fan impeller blades and discharge radially outwardly through the radiator core or, alternatively, the fan may be a suction type wherein cooling air is drawn radially inwardly through the toroidal radiator core and discharged axially from one axial side of the heat exchange apparatus.
However, automotive cooling system engineers have not had much success in the adaptation and utilization of toroidal radiators in motor vehicle engine cooling systems prior to the present invention. The typical installation took the form of a round or toroidal radiator, a venturi type fan shroud, and a blower type, axial flow fan, as disclosed in U.S. Pat. No. 3,800,866. In such a typical installation, cooling air is drawn axially from one side of the round radiator by the fan, which is located coaxially with respect to the round or toroidal radiator, and is discharged, in a generally axial direction, under pressure, to the plenum chamber or space defined by the radially innermost cylindrical face of the toroidal radiator core. Inasmuch as the cooling air passageways of a conventional toroidal radiator core extend radially through the core it is necessary to provide elaborate baffle means or other air flow guiding means for "bending" the air stream to effect a change in the direction of fan-generated air stream from a generally axial direction to a generally radial direction in an efficient manner. The resulting direction change of the air stream, however, was accompanied by a diminution of the velocity pressure of the air stream. Furthermore, the velocity of the air flowing over the radiator core was non-uniformly distributed over such available heat exchange surface. As a consequence, the use of toroidal radiators in conjunction with motor vehicle engine cooling systems has not become widespread as initially contemplated.